Some of the greatest works of art and creativity come from "excessively" introverted people.
I'm one clinician in the boat that feels that it is not such a bad thing. It is the anger, lack of role models (especially fathers), soured development, and the devaluing of introversion in American society that may lead to resentments and boil into a murderous rage. Throw in a largely multicultural society in contemporary America in which one's identity is compromised, if not ever truly acknowledged and celebrated, and bingo.

You say Oswald was grandiose, narcissistic, and had an inflated sense of self. Ok, but if one goes on to accomplish things that change history, are not they vindicated by those beliefs?
Some people are born to make history and do great things. Some know it intuitively for a long time before it happens. We often mistake it as narcissism, arrogance, or 'grandiosity'. This only diminishes their victories. Many haughty individuals never accomplish much, and die penniless with poor reputations and few friends. But those who live up to what they believe about themselves, regardless of the morality of their behavior, are worthy of closer examination.

Like him or not, Oswald was a catalyst for change in the 20th century, and likely even changed the world more than Kennedy ever hoped to. Sad, but true.

PS, the Italian Carcano modello 1891/38 is NOT a "single shot" rifle. It is a bolt-action, semi-automatic carbine that has a 6-round charger fitted inside an integral magazine. An experienced shooter (like Owald) can fire all 6 shots within 15 seconds.